Holstein, N.

Konys, J.

Krauss, W.

Lorenz, J.

English

KITopen

www.kit.edu KIT – University of the State of Baden-Württemberg and National Research Center of the Helmholtz Association INSTITUTE FOR APPLIED MATERIALS |  MATERIAL PROCESS TECHNOLOGY |  CORROSION DEPARTMENT    Electro-chemical processing for tungsten fabrication and joining by layer deposition  W. Krauss, J. Konys, N. Holstein, J. Lorenz Outline:  •  Motivation  •  Challenges in W handling •  Machining by electro-chemical dissolution (ECM) •  Layer deposition / joining from aqueous systems •  Innovative deposition from aprotic electrolytes •  Conclusions  Challenges to Developing W-Based Materials for Fusion Applications  UCSB, Santa Barbara, CA, USA, February 13 – 15, 2012  W. Krauss   IAM-WPT / KOR 2 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining                     Motivation for Electro-Chemical Processing Castellation  Application:  • Machining • Joining   • Composites W, Cu Steel, SS  FW coating W-scales Oxidation protection Al, Si, Y T-permeation and  corrosion barriers Al, Er, W-based Eurofer Tungsten Activation control Cleaning of EDM processed BU’s  Divertor development  Blanket development W. Krauss   IAM-WPT / KOR 3 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Mock up # 4 Motivation for Electro-Chemical Processing of W  Typical defects and failures of W parts Secondary failures, growing under HHF load Primary machining defects HHF results defined needs for development in W-processing and joining    • Smooth surfaces  • No defects from machining  • No sharp edges  • Adapted fillers for brazing Crack growth at machining defect Post HHF analyses of mock-up.  Machining defect caused failure KIT-Efremov coop. Filler behavior W. Krauss   IAM-WPT / KOR 4 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining                     Anodic reaction W-dissolution Surface treatment Electro-polishing S-ECM Machining ECM C-ECM, M-ECM Cathodic reaction Deposition Layer deposition brazing e.g. by Ni, Cu, Pd protic Deposition aprotic e.g. W or Ta Electro-Chemical Reactions 0,00010,0010,010,11101001000-0,75 -0,5 -0,25 0 0,25 0,5 0,75 1 1,25 1,5 1,75 2 2,25 2,5 2,75 3 3,25E / V (Hg/HgSO4)i / mAcm-2 pH = 12,4 pH = 12 pH = 11 pH = 10 pH = 9 pH = 9 pH = 8 pH = 7 pH = 7 pH = 6 pH = 5 pH = 3 pH = 1i = f(pH)System: W / TCEE  / Ptv = 1 mV/s, 1000 U/min, d = 16 mmApplication Basic investigation W. Krauss   IAM-WPT / KOR 5 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining                     Processed Cathode = ECM  working tool Anode =  workpiece - + - + - + workpiece de =  rkpiece cathode = ECM working tool, negative imagevertically mobileanode = workpieceelectrolyteagitation by microstep-motorframeworkcathode guiding+-ECM Requirements  Electrolyte development  M-ECM: anode mask process C-ECM: cathode tool  ECM Advantages No cracks by ECM process Surface polishing residue-free metal removal                              M-ECM for Slot array :  UV-mask Novolak C-ECM scheme C-ECM 2 H+ + 2e- → H2 Me → Me2+ + 2e- M-ECM MAIN DIFFERING FEATURES M-ECM C-ECM Technique Conventional installation Complex facility Parameters Current x time = charge Charge + distance + steprate + convection Cathode passive counter electrode  active shaping component (by step motor) Tool design 2-dim. mask (positive)  3-dim. electrode (negative) Transformation +2-dim  g +3-dim  -3-dim   g +3-dim ECM for 3-D structuring Mask processing UV - lithography Electro-chemical  Etching Structured workpiece h n 365 nm + - W. Krauss   IAM-WPT / KOR 6 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining 6   | J. Konys | IMF III/KOR | 10.03.2009 Smaller distance   tool – work piece W machining – impact on quality   Parameter dependencies Higher frequency of pulsed DC power  Hz: 10000 1000 500 100         10        0C-ECM:Edge steepness asFunction of pulse frequency nDesiredflank profile-1100-1000-900-800-700-600-500-400-300-200-1000100200300-2500250500750100012501500175020002250250027503000Abstand AE-GE / mmE / mV (Hg/HgSO4) 200 mA/cm2 100 mA/cm2 150 mA/cm2   50 mA/cm2E = d(AE-GE)System: W / SL1 / Pti = 200 mA/cm2, 1500 U/min, d0 = 3 mmMobility control / reduction  Conductivity of electrolyte 0,00010,0010,010,11101001000-0,5 -0,25 0 0,25 0,5 0,75 1 1,25 1,5 1,75 2 2,25 2,5Potential E [V vs. NHE]i [mAcm-2] pH = 12 pH = 11 pH = 10 pH = 9 pH = 8 pH = 7 pH = 6 pH = 3 pH = 1Linear Scanning Voltametry (LSV)Sytem: W / TCEE / PtScan rate: 1 mV/secW. Krauss   IAM-WPT / KOR 7 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Tungsten by C-ECM (Anodic dissolution)  C-ECM demonstrator cathodes Generated W-structures Parallel grooved structure  Angled structure  W. Krauss   IAM-WPT / KOR 8 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Functional layers by cathodic deposition        W – steel  W-W joining W thimble Steel Cu-layer Requirements: Example for not adjusted filler – matrix combination Development paths in EC:    Oxidation protection by scales e.g. Ta, Si, Cr, Y, Zr, La, Al, Eu Diffusion barriers e.g. W, Ta, V, Cr, (Ni), Fe Fillers based on e.g. Ti, V, Pd, Zr, (Ni), Cu, Fe       50 cm  (1/2 plate length) 20.8 cm UCSD Malang et al. Brazing lacks in the past •  No wetting •  Incomplete wetting •  Not adapted filler composition •  Embrittlement W. Krauss   IAM-WPT / KOR 9 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Electro-chemistry for coating development EC measurements of protic  and aprotic metal  deposition systems Organic electrolytes:      EMIM-Cl (Ethyl-Methyl-Imidazolium-Cl)   PC  (Propylencarbonat)  Elements with relevance to joining and electro-chemical deposition W. Krauss   IAM-WPT / KOR 10 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining EDM - worked Turning  etched Surface activation by K3[Fe(CN)6] * KOH     small roughing  HNO3  (conc.)  * HF     high temp.              KOH                            polishing, low adherence NaOH  *  KMnO4             HCl cleaning HCl     *   H3C-COOH  roughing NH3     *   NaNO3              polishing, current Turning  etched Turning Interference EDM  etched Cracks Turning EDM Raw material Defects from working emphasized  Clean, oxide free surface  for coating Coatings from aqueous systems Surface activation W. Krauss   IAM-WPT / KOR 11 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining EDM worked part     after heat treatment, 700°C , vacuum Electrolyte:  1.3 M Nickel sulfamate Ni(SO3NH2)2 T = 52 °C, pH = 3.5,  i = 10 mA/cm²,D = 12 µm/h Constant thickness on edge Coatings from aqueous systems Advantage of homogeneous layers Tungsten Ni interlocking in interface layer Parts by turning     EDM initiated cracks contrasted W. Krauss   IAM-WPT / KOR 12 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Resin W –steel joining with Ni and Cu coatings from aqueous systems 050100150200250300CountsN[arb.units]50 100 150 200Testing distance x [µm]Cr (Eurofer)Fe (Eurofer)Ni (Functional scale)Cu (Brazing alloy)WTungsten Eurofer Copper Ni Ni Functions:  W – Ni interlayer as alloying support  Ni – Eurofer surface activation  Cu   filler metal  Brazing by Ni – Cu alloying W – steel joint Eurofer Tungsten Cu Brazed at 1100°C W. Krauss   IAM-WPT / KOR 13 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Resin W – W brazing with Ni and Cu coatings W – W joint Brazed at 1100°C Ni – Cu – Ni scales Tungsten Tungsten Tungsten Cu filler W W Cu Ni Ni 0100200300400500600700800CountsN[arb.units]40 60 80 100 120 140 160 180 200Testing distance x [µm]Ni Functional scaleCu Filler metalW Work pieces4-2-10 W-W-Cu 10MW. Krauss   IAM-WPT / KOR 14 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Coatings from aqueous systems Joining of W-W by Cu and Pd  No miscibility Direct reactive joining of W-W  not possible by Cu Functional layer Pd required  W - Pd - Cu  Pd-W  Pd-Cu  Cu is appropriate as filler metal due to fully miscibility with Pd Cu+W  W. Krauss   IAM-WPT / KOR 15 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Pd layer Cu layer Pd layer Cu + Pd layers T = 1100°C, t = 10 min in Ar  + cooling in air As deposited on W After brazing Coatings from aqueous electrolyte systems W coated by Pd + Cu W - Pd - Cu + W - Pd Pd on W as reactive interlayer for Cu brazing W after chemical conditioning Cu substrate Pd deposited on Cu Electrolyte testing W. Krauss   IAM-WPT / KOR 16 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining  uniaxial forcing Mechanical characterization of joints from aqueous electrolytes Shearing strength tests of brazed specimen  1100°C First shear tests show applicability of test method, but further development and optimization is needed Introduction Conclusion W. Krauss   IAM-WPT / KOR 17 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining               Brazing material breaks amongst the brazed Cu bulk Specimen after test, optical overview SEM SEM Planned: Eurofer-Pd-Cu-Pd-Eurofer Preliminary specimen as model system  steel-Ni-Cu-Ni-steel for test qualification Mechanical characterization of joints from aqueous electrolytes Shearing strength tests of brazed specimen  Introduction Conclusion W. Krauss   IAM-WPT / KOR 18 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Deposition from aprotic systems N NRX-+Al3+ + 3 Cl- or W6+ + 6Cl- →  EMIM-AlCl4 or EMIM-WCl6  AlAlKKFWCl6 Only Al Properties of organic aprotic electrolyte systems W. Krauss   IAM-WPT / KOR 19 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining                     Ionic liquids as electrolyte for W deposition - Ethylmethylimidazolium-chloride + WCl6     EMIM-Cl, 80°C EMIM-Cl + Salt  +  DC Deposited metal EMIM-Cl, RT EMIM-Cl + Salt IL  melting Scale Deposition Mixing IL + salt W. Krauss   IAM-WPT / KOR 20 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining W layer in vertical SEM view Coatings from organic electrolytes (IL) Tungsten layer on Eurofer steel  Deposited at 120°C Electrolyte (IL) EMIN-Cl + WCl6 W layer in SEM cross section Development needs for W, Ta .. •  Evaluation of solvent / salt compatibility •  Analyses of current modes •  Analyses of electrolyte composition •  Adhesion •  Morphology W on Eurofer W scale 15 μm Eurofer resin W. Krauss   IAM-WPT / KOR 21 Developing W-based materials, Santa Barbara, USA, Feb. 2012 Electro-chemical processing for tungsten fabrication and joining Conclusions Electro-Chemical Machining (ECM) of tungsten    ECM is a tool to machine W successfully without chemical passivation  Quality improvement realized by short DC pulses and gap control  Demonstrators fabricated by C-ECM with 10 kHz pulse generator  Electro-chemical deposition for joining and functional scales  Aqueous systems:   Successfully performed W – W and W-steel joining by deposited Cu, Ni  Multilayer deposition on W parts under execution to increase operation     temperature  Substitution of model metal Ni successfully demonstrated by Pd plating  Mechanical shear tests showed well adherence of filler at bulk  Organic systems:   IL systems applicable for deposition of refractory metals 

Electro-chemical processing for tungsten fabrication and joining by layer deposition

https://publikationen.bibliothek.kit.edu/230086651/3816017

Electro-chemical processing for tungsten fabrication and joining by layer deposition

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